P-release kinetic as a predictor for P-availability in the STYCS Trials
In my Internship I studied the current GRUD, particularly Mg, P and K
Fertilizer requirement models imply \(Y\sim STP + Clay\) & \(P-\text{Export}\sim STP + Clay\)
Currently only stationary measurement of STP are considered
Could a kinetic desorption-model better explain the soil status and yield data?
The net-desorption was modeled using a first-order kinetic equation:
1. The Rate of Release: The change in P over time is proportional to the remaining desorbable P. \[\frac{dP}{dt}=k \times (P^S-P)\]
2. The Solution: When solved, this gives us the equation for the curve: \[P(t)=P^S \times (1-e^{-kt})\]
Relevant Variables
Soil Variables:
Yield Variables:
The following random structure was chosen:
(1|year) + (1|Site) + (1|Site:block) + (Treatment|Site)
| Predictor | PS | k | log(k*PS) | CO2 | AAE10 |
|---|---|---|---|---|---|
| (Intercept) | -1.772 | -0.425 | 0.039 | -0.536 | -0.532 |
| Alox | -0.660 | -1.204 | -0.034 | -0.319 | |
| Feox | 0.020 | -0.571 | -0.164 | -0.138 | |
| soil_0_20_clay | 1.798 | -1.733** | 0.611 | -0.007 | -0.121 |
| soil_0_20_Corg | 1.044** | -0.412 | 0.166 | 0.232 | |
| soil_0_20_pH_H2O | 0.000 | -0.280 | 0.094 | 0.075 | 0.057 |
| soil_0_20_silt | 0.252 | 0.113 | -0.084 | 0.012 | |
| R2m | 1.000 | 0.204 | 0.224 | 0.125 | 0.280 |
| R2c | 1.000 | 0.963 | 0.976 | 0.724 | 0.832 |
Observation
| Predictor | Yn-STP-CO2 | Yn-STP-AAE10 | Yn-STP-GRUD | Yn-Kinetic | Yr-STP-CO2 | Yr-STP-AAE10 | Yr-STP-GRUD | Yr-Kinetic |
|---|---|---|---|---|---|---|---|---|
| (Intercept) | 0.012 | 0.007 | -0.109 | 0.156 | -0.323 | -0.257 | -0.306 | -0.119 |
| k | 0.166 | -0.018 | ||||||
| k:log(PS) | -0.012 | 0.016 | ||||||
| log(PS) | 0.066 | 0.010 | ||||||
| log(soil_0_20_P_AAE10) | 0.067* | 0.432** | 0.037 | 0.046 | ||||
| log(soil_0_20_P_CO2) | 0.027 | -0.128 | -0.001 | -0.040 | ||||
| log(soil_0_20_P_CO2):log(soil_0_20_P_AAE10) | 0.149* | -0.021 | ||||||
| R2m | 0.012 | 0.084 | 0.291 | 0.019 | 0.000 | 0.011 | 0.020 | 0.002 |
| R2c | 0.083 | 0.361 | 0.436 | 0.045 | 0.618 | 0.698 | 0.696 | 0.807 |
Observation
| Predictor | CO2_Pexport | AAE10_Pexport | Grud_Pexport | Kin_Pexport |
|---|---|---|---|---|
| (Intercept) | 0.012 | -0.002 | 0.119 | 0.596 |
| k | -0.014 | |||
| k:log(PS) | 0.080 | |||
| log(PS) | -0.018 | |||
| log(soil_0_20_P_AAE10) | 0.025 | -0.015 | ||
| log(soil_0_20_P_CO2) | 0.087 | 0.131 | ||
| log(soil_0_20_P_CO2):log(soil_0_20_P_AAE10) | 0.011 | |||
| R2m | 0.012 | 0.001 | 0.016 | 0.004 |
| R2c | 0.654 | 0.685 | 0.796 | 0.789 |
Observations
| Predictor | CO2_Pbalance | AAE10_Pbalance | Grud_Pbalance | Kin_Pbalance |
|---|---|---|---|---|
| (Intercept) | 0.569* | 0.315 | 0.610* | 1.086* |
| k | 0.155 | |||
| k:log(PS) | -0.151 | |||
| log(PS) | 0.341*** | |||
| log(soil_0_20_P_AAE10) | 0.009 | 0.009 | ||
| log(soil_0_20_P_CO2) | -0.023 | -0.029 | ||
| log(soil_0_20_P_CO2):log(soil_0_20_P_AAE10) | 0.030 | |||
| R2m | 0.001 | 0.000 | 0.006 | 0.122 |
| R2c | 0.590 | 0.762 | 0.596 | 0.699 |
Observation
Thank you for your attention